Electric circuit contacts



June 18, 1957 T. R. STUELPNAGEL ETAT. 2,796,491

ELECTRIC CIRCUIT CONTACTS Filed March l, 1954 United States Patent ff)ELECTRHC CRCUIT CONTACTS Thomas R. Stuelpnagel, Inglewood, and Pol R.Verbeke,

Los Angeles, Calif., assignors to Hughes Tool Company/,Houtem Tex., acorporation of Delaware Application March 1, 1.954, Serial No. 413,302

Claims. (Cl. 20G-.405)

of contact failure which must be overcome is the formation of spireswhich attends the transfer of metal to the positive contact when thecontacts are separated.

'H-In many prior art circuit contact devices, protective circuits areconnected between the contacts to suppress arcing .and sparking when thecontacts are separated. This provision is elective to reduce the volumeof metal transfer, but it does not prevent the formation of yslenderspires, which lengthen progressively with the number of make-and-breakoperations. These spires may ultimately form a link zbetween thecontacts `which cannot be broken with the force available, and thispossibility necessitates frequent inspection and maintenance to keep thecontacts inoperation. It is for these reasons that, in many instances,bulky and 'costly electronic amplifying systems must be relied on todevelop the power required to control electric circuit operations.

`,The present invention overcomes the rabove-mentioned disadvantages andprovides means whereby sensitive contacts may be employed where greatreliability of operation is required 'and where .available space fornecessary electrical components is at `a premium. fIn accordance withthis invention, a cylindrical contact surface is continuously orintermittently rotated. A movable contact is spaced from the peripheryof the rotating contact, against which it may be brought intoengagement. Bearing against the periphery of the rotating contact is anelement for keeping the surface of the rotating contact smooth .andclean, which element causes a continuous shearing action against thecylindrical contact surface when the Ilatter is rotating, to therebysubstantially reduce build-up of metal transfer 'and prevent spireformation.

It is, therefore, an object of this invention to provide rotatablecircuit contact means capable of reliable operation over a longoperating life by continuously removing spires formed by contactactions, and which contact means is suitable to be controlled with aminimum amount of power.

lt is another object of this invention to provide electric circuitcontact means comprising .a minimum number of -component parts of simpledesign, capable of providing reliable operation without attention, andwith which sensitive contact operation over a long cont-act 'life isrealized.

`The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will be betterunderstood from the following description considered in connection withthe accompany- 2,796,491 Patented June 18, 1957 2 ing drawings, in whichpreferred embodiments of the invention are illustrated by way ofexample. 'The scope of the i-nvention is pointed out in the appendedclaims: In the drawings:

Fig. 1 is a perspective view of electric circuit control apparatusemploying contact means in accordance with this invention; and

Fig. 2 is a modification of the arrangement .shown in Fig. 1.

Referring tothe drawing, in which like reference characters indicatelike parts throughout, and referring more particularly to =Fig. 1, acontrol circuit 10 is connected to the terminals 12 of an electromagnet14. The electromagnet 14 is provided with a movable armature 16. Anelectric -circuit contact arm 18 having a contact portion 21 is aflixedto or integral with armature 16 for vmovement therewith whenelectromagnet 14 is energized.

Contact arm 18 is positioned such that contact portion 21 is adjacentthe 'cylindrical contact surface 20 of a rotary contact element 19. Aspring 17 is attached to the armature y16 and the frame of electromagnet14 to normally bias the member 18 out of contact with the surface 20.When armature 16 is attracted by electromagnet 14, contact 271 is-brought into engagement with surface 2 0. Element 19 is preferably aslip-ring -type of contact and is `supported on and insulated from theshaft 22 of a motor 24.

vBearing against surface 2.0 is a Contact 26 which is aV spring metalelement arranged to maintain constant .shearing engagement againstsurface 20. When a circuit is connected between contact 2,6 and contact18, and when electromagnet 14 is energized to bring contact 21 to bearupon surface 2l), rotation of element 19fby motor 24 causes a shearingaction by contact 26 which action prevents the aforementioned spirebuild-up by `scraping off any minute metal particles that are depositedon surface 2.0 from contact 18.

A load circuit 2,8 and a |power source, indicated as ,a batt-ery 30, areserially connected between contact 26 and 'cont-act arm 18. Motor `24may vbe supplied with energy either from battery 30 or from 'a :separatepower source `32, as indicated schematically in the drawing by theprovision of a switch 34 for Selecting the source of energy for drivingmotor 24.

A conventional contact protection circuit 35 is connected between thecontact 26 land contact arm 18. `Circuit 35 is `designed to give maximumprotection against arcing and sparking which the particular load circuit28 tends to cause.

Fig. 2 illustrates a modification of the arrangement above described,including power relays controlled yby a sensitive relay foralternatively energizing two control circuits and for performing thefunction of the motor 24 of tFig. 1. 'Referring to Fig. 2, a secondrotary contact element `19 is supported on shaft 22 and spaced fromelement `19. A movable contact arm 18 having a contact portion I21 xedto armature 16, is .positioned such that contact 21 is adjacent theperipheral surface 20 'of element 19. Armature 16 is arranged foractuation in opposite directions Iby a polarized electromagnet 14. Whenarmature 16 is moved in one direction, contact 21 engages surface 20,and movement of the armature in the opposite direction causes contact21' to engage the surface 20'. A contact 26 bears against the peripheralsurface 20 of element 19 to perform the same function 'as abovedescribed for contact 26 in Fig. 1.

Contacts 21 and 21', rotary elements 19, 19 are connected between therespective windings of a pair of power electromagnets 48, 48', and asource such as a battery 30. The power electromagnetsV 48, 48' areprovided with The surface of contact 21 is .020l in diameter.

3 respective armatures arranged to actuate relatively large powercontact assemblies 50.

A pair of ratchet wheels 42, 42 are secured to the shaft 22. Pawls 44,44 are supported on armatures `tact 26 and surface 20 for removing anymicroscopic spires resulting from the engagement of contact 21 withsurface 20. Reversal ofrcurrent through coil 14 causes armature 16 tomove in the opposite direction, whereupon contact 21 disengages surface20 and contact 21' engages surface Electromagnet 4S is thus energized toattract armature 46 and pawl 44' to rotate ratchet wheel 42 and cause ashearing action between contacts 26 and surface 20.

The power contacts 50 are connected to control the energization of anappropriate utilization device such as a power load 52. By thisarrangement, the sensitive relay 14 energizes the power relays 48, 48 tocontrol substantially any desired amount of power.

In one practical arrangement of the above-described Vcontact structure,the separation of contact 21 from surface 20 is .002 when theelectromagnet 14 is deenergized. The spring 17 was adjusted to provideapproximately three grams of force to separate contact 21 from surface20. This embodiment with member 19 rotated at approximately threerevolutions per minute, performed more kthan 20,000,000 cycles ofmake-and-break operations withoutl substantial change in the physicalcondition of the contact surfaces and without the necessity of cleaningor other attention.

From the foregoing description, it will be apparent thatV the presentinvention provides an improved type of electrical contact deviceparticularly suitable for sensitive contact operation, presentingsubstantially no maintenance problems, and capable of a degree ofreliable operation drical contact having a peripheral surface; a movablecontact constructed and arranged such as to make and 50 break contactwith said peripheral surface; first means energizable by the low powercircuit for actuating said movable Contact; second means responsive toactuation of the movable contact for rotating the cylindrical contact;land a resilient element having an end portion in shearing engagementwith the peripheral surface of said cylindrical contact such that saidshearing engagement is effective, when the cylindrical contact isrotated, for scraping olf metal deposited on the peripheral surface as aresult of the movable contact making and breaking contact with thecylindrical contact.

2. A sensitive contact system for energizing an electrical circuit froma low power control circuit, said con- -tact system comprising: arotatably supported cylindrical contact having a peripheral surface; amovable Contact vconstructed and arranged such as to make and break-contact with said peripheral surface; a resilient element having an'endportion in electrically conductive but shearing engagement with saidperipheral surface such that rotation of the cylindrical contact iseective for scraping off metal deposited on said surface as a result forrotating said cylindrical contact, said means including anelectromagnetic element, a source of electrical energy, and an actuatingcircuit embracing the cylindrical contact, the movable contact, theresilient element, said electromagnetic element, and said source ofenergy.

3. A sensitive contact'system for energizing an electrical circuit froma low power control circuit, said contact system comprising: a rotatablysupported cylindrical contact having a peripheral surface; a movablecontact constructed and arranged such as to make and break 0 contactwith said peripheral surface; a resilient element having an end portionin electrically conductive but shearing engagement with said peripheralsurface such that rotation of the cylindrical contact is effective forscraping olf metal deposited on said surface as a result of the 5movable contact making and breaking contact with the cylindricalcontact; a control circuit embracing electromagnetic means for actuatingthe movable contact; first means responsive to actuation of the movablecontact for rotating said cylindrical contact, said first means includ-0 ing an electromagnetic element adapted to rotate the cylindricalcontact, a first source of electrical energy, and an actuating circuitembracing the resilient element, the movable contact, the cylindricalcontact, said electromagnetic element, and said source of energy; andsecond means for rotating said cylindrical contact independently of thefirst means, said second means including v a second source of electricalenergy and a selectively operable switch adapted for disconnecting theelectromagnetic element of the rst means from thefirst source l ofelectrical energy and for connecting said magnetic element to saidsecond electrical energy source. 4. A sensitive contact system forenergizing an electrical circuit from a low power control circuit7 saidconltact system comprising: a cylindrical contact having a peripheralsurface; a movable contact arranged such as to make and break contactwith said peripheral surface; first means energizable by the lower powercontrol circuit for actuating said movable contact; a ratchet wheel; ashaft supporting the ratchet wheel and the cylindrical contact such thatrotation of said wheel effects rotation of said cylindrical Contact; apawl constructed and arranged for rotating the ratchet wheel; secondVmeans responsive to the actuation of said movable contact for actuatingsaid ratchet wheel; and a resilient element having an end portion inshearing engagement with the peripheral surface of said cylindricalcontact such that said end yportion is effective, when the cylindricalcontact is rotated, for scraping oif metal deposited on the peripheralsurface by the contact making and breaking action of the movable contactwith said peripheral surface.

5. A sensitive contact system for energizing an electrical circuit froma low power control circuit; said contact system comprising: a rotatablysupported cylindrical contact having a peripheral surface; a movablecontact constructed and arranged such as to make and break contact withsaid peripheral surface; a resilient element having an end portion inelectrically conductive but shearing engagement with said peripheralsurface such that rotation of the cylindrical contact is effective formeans responsive to actuation of the movable contact for rotating thecylindrical contact, said means including a ratchet wheel, a shaftsupporting the ratchet wheel and the cylindrical contact such thatrotation of said wheel effects rotation of the cylindrical Contact, apawl 0. constructed and arranged for rotating the ratchet wheel, anelectromagnetic element adapted for actuating sa1d pawl, a source ofelectrical energy, and an actuating circuit embracing the resilientclement, the rotating contact, the movable contact, the electromagneticelement,

and the source of electrical energy.

(References on following page) References Cited in the le of this patent1,610,555 2,422,842 UNITED STATES PATENTS 2,572,105 232,806 Davis Oct.5, 1880 988,442 Burnham Apr. 4, 1911 1,062,380 Apple May 20, 1913992,597

6 Kindl Dec. 14, 1926 Molyneux et a1. June 24, 1947 Bronstein Oct. 23,1951 FOREIGN PATENTS France July 11, 1951

